The present disclosure relates to seals, and more particularly to seals for turbomachinery, such as for example seals between a case and rotor turbine blades in a gas turbine engine.
Leakage of flow-path air may occur in turbomachinery between the tips of a rotating blade structure and the outer static structure. This leakage has a negative effect on performance, efficiency, fuel burn, and component life. Turbomachinery with a wide operating range, such as an aircraft gas turbine engine, conventionally requires large tip clearances due to the mismatch in thermal responses between the rotating structure and the static structure. A static structure with a rapid thermal response rate will experience significant closure to the rotating structure during rapid decelerations. Conversely, a static structure with a slow thermal response will experience significant closure to the rotating structure during rapid accelerations. Further, the rotating blade structure generally includes two rotating structures, the blade airfoils that generally have fast thermal response rates and the rotor disk, that generally responds slower.
As a result, both configurations require large tip clearances throughout the operating range. Large tip clearance can equate to lower efficiency. By minimizing the tip clearance between the rotating and static structures efficiency can be improved. In some designs, an annular control ring is provided on the outer static structure to control the thermal response of the blade outer air seal system, at least under some operational conditions.
Such conventional methods and systems have generally been considered satisfactory for their intended purpose. However, there is still a need in the art for an improved sealing system. The present disclosure provides a solution for this need.